Исследование формирования, структуры и физических свойств нанопроволок сложного состава тема диссертации и автореферата по ВАК РФ 00.00.00, кандидат наук Долуденко Илья Михайлович

• Долуденко Илья Михайлович
• кандидат наук
• 2023

Оглавление диссертации кандидат наук Долуденко Илья Михайлович

ВВЕДЕНИЕ

Научные результаты и публикации

Заключение

Список используемой литературы

Приложения

Приложение 1: статья «Structure of Cu/Ni nanowires obtained by matrix synthesis»

Приложение 2: статья «Structure and Magnetic Properties of Nanowiresof Iron Group Metals Produced by Matrix Synthesis»

Приложение 3: статья «Specific features of obtaining of metal nanowires by replication of pores of track etched membranes»

Приложение 4: статья «Fabrication of Cylindrical Magnetic Nanoparticles

for Functionalization of Polyelectrolyte Microcapsules»

Приложение 5: статья «Aspects of Pore Filling in Synthesis of FeNi Alloy Nanowires Using Track-Etched Membranes»

Приложение 6: Статья: Electrical properties arrays of intersecting of nanowires obtained in the pores of track membranes

Приложение 7: Патент № 2724264 «Способ получения наностержней никеля с регулируемым аспектным отношением» Долуденко И.М., Загорский Д.Л., Трушина Д.Б., Бурмистров И.А

ВВЕДЕНИЕ

Введение диссертации (часть автореферата) на тему «Исследование формирования, структуры и физических свойств нанопроволок сложного состава»

Актуальность темы

В настоящее время все возрастающий интерес проявляется к наноматериалам и структурам на их основе. Исследованию возможностей их получения, изучению их структуры и свойств посвящены многие работы как фундаментального, так и прикладного характера. Многообразие методов получения, характера и свойств наноструктур обеспечивает широкое поле их применений.

Одним из типов наноструктур, обладающих большим потенциалом в практическом применении, являются одномерные наноструктуры, или нанопроволоки (НП). Существует ряд методов их получения. Одним из них является матричный синтез. Основная идея данного метода заключается в заполнении заранее подготовленной матрицы необходимым материалом. При этом на данный момент большой интерес представляет получение одномерных магнитных наночастиц. Это связано с все возрастающими темпами изучения наноразмерных, квантовых и спиновых эффектов, а также потребностью в новых материалах и структурах для применения их в химии, радиоэлектронике, микроэлектронике и медицине.

Несмотря на то, что метод матричного синтеза известен с 90-х годов двадцатого века, многие аспекты методик получения, особенности структуры и функционал получаемых частиц не изучены в полной мере. Большая часть работ посвящена изучению отдельных режимов получения, а не их совокупности для установления связи и возможности прогнозирования получаемой структуры и свойств. Установление зависимостей структуры и, как следствие, свойств наноструктур от режимов их получения, а также создание способов контролируемого изменения как геометрических, так и структурных параметров позволят существенно приблизить исследования в данной области к практическому их применению в различных областях

науки и техники, что определяет актуальность темы настоящего исследования.

Степень разработанности темы исследования

Как уже отмечалось выше, метод матричного синтеза основан на заполнении заранее подготовленной матрицы необходимым материалом. В качестве матрицы для создания одномерных наночастиц чаще всего используются пористый оксид алюминия (ПОА)1 и трековые мембраны (ЩТ. Данные

типы матриц отличаются способами получения и, как следствие, физико-химическими свойствами, геометрией и совместным расположением пор в объеме матрицы, а также, что самое главное, возможностью контролируемо управлять и изменять отдельные параметры. Так, ТМ, имея в основе полимерную пленку, обладают гибкостью и эластичностью, что позволяет применять структуры на их основе в элементах микроэлектроники и радиоэлектроники3. Процесс их получения подразумевает возможность контролируемо изменять диаметр пор и, соответственно, диаметр получаемых наночастиц. Стоит отметить, что подобные изменения диаметра могут быть независимы от плотности пор, чего в полной мере нельзя достичь при создании матриц из ПОА4. Еще одним преимуществом ТМ является возможность изменения угла наклона пор по отношению к плоскости матрицы при ее получении с сохранением заданных параметров по всему объему. Помимо этого, сам процесс получения ТМ

1 Masuda H., Fukuda K., Quantitative characterization of acid concentration and temperature dependent self-ordering conditions of anodic porous alumina, [текст]// Science. V. 268 1995. P. 1466.

2 Фролов К. В., Загорский Д. Л., Любутин И. С., Коротков В. В., Бедин С. А., Сульянов С. Н., Артемов В. В., Мчедлишвили Б. В., Синтез, фазовый состав и магнитные свойства нанопроволок железа, полученных в порах полимерных трековых мембран, [текст] // Письма в ЖЭТФ, том 99. выпуск 10. 2014, С. 656.

3 Ohgai T. Electrodeposited Nanowires and Their Applications / Ed. Lupu N. InTech: 2010. 61 P.

4 Pyatkov E. S. , Berekchiyan M. V., Yeliseyev A. A., Lukashin A. V., Petukhov D. I., Solntsev K. A., Electrochemical Detection of Barrier Layer Removal for Preparation of Anodic Alumina Membranes with High Permeance and Mechanical Stability [текст]// Inorganic Materials: Applied Research V. 9 2018, p. 82-87

является поточным и отработанным в Объединенном институте ядерных исследований (ОИЯИ, Дубна), при этом сохраняется геометрическое расположение пор в матрице и их селективность по диаметру, что является важным обстоятельством при создании наночастиц, например, для медицинских применений5. Исходя из вышеописанного, в качестве матрицы в настоящей работе были выбраны трековые мембраны.

Основным способом заполнения матриц для получения магнитных НП является метод электрохимического осаждения. Он применим к обоим типам матриц - и ПОА, и ТМ - после их предварительной подготовки. Данный метод отличается возможностью изменять структурные параметры получаемых материалов, тем самым изменяя их свойства, а также получать широкий спектр материалов НП 6'7.

Весьма перспективными материалами для создания магнитных наночастиц являются сплавы на основе железа, а именно сплавы с кобальтом или никелем8. Для объемных материалов известно, что, варьируя соотношения указанных элементов, можно получать совершенно разные магнитные свойства. Так, сплав Fe20Ni80 (пермаллой) является магнитомягким, а сплав с эквиатомным соотношением железа и кобальта -магнитотвердым сплавом. Представлялось интересным выяснить, характерны ли вышеуказанные магнитные свойства для наноразмерных структур этих сплавов. Для этого необходимо было разработать методы контроля состава и структуры получаемых нанообъектов. Стоит отметить, что метод электрохимического осаждения позволяет варьировать

5 Switzer J. A., Hodes G., Electrodeposition and chemical bath deposition of functional nanomaterials [текст]// Annu. MRS Bulletin V.35, 2010, Issue 10: Electrodeposition and Chemical Bath Deposition of Functional Nanomaterials , pp. 743 - 750

6 Alonso J., Khurshid H., Sankar V., Nemati Z., Phan M.H., Garayo E., Garcia J.A., Srikanth H., FeCo nanowires with enhanced heating powers and controllable dimensions for magnetic hyperthermia, [текст]// J. Appl. Phys., V.117 (17), 2015, 17D113.

7 Elbaile L., Crespo R.D., Vega V., Garcia J.A., [текст]// J. Magnetostatic Interaction in Fe-Co Nanowires, Nanomater. V. 13, 2012, 198453.

8 Atalay F.E., Kaya H., Atalay S., Tari S, Influences of deposition time and pH on magnetic NiFe nanowires fabrication. [текст]// J. Alloys Compound, V. 469, 2009, 458.

соотношение ионов осаждаемых металлов в электролите, это соотношение не всегда сохраняется в осажденном материале. Так, для процесса объемных материалов характерен эффект аномального со-осаждения железа. Он заключается в том, что при электрохимическом осаждении из растворов, содержащих ионы нескольких металлов, одни из которых Fe+2 , соотношение осажденных атомов различных ионов будет отличаться от соотношения ионов в электролите в сторону увеличения железа. Вопрос о проявлении данного эффекта при осаждении в поры трековых мембран осложняется накладываемыми диффузионными ограничениями пор матрицы. При этом возникает ряд вопросов, например, таких как, будет ли данный эффект сохраняться при осаждении в ограниченном объеме, как данный эффект будет зависеть от типа осаждаемых ионов, их соотношения и скорости осаждения.

Еще одной особенностью электрохимического метода заполнения пор матриц, является возможность послойного осаждения ряда металлов; она реализуется благодаря разности равновесных потенциалов осаждения различных металлов9. Материал с меньшим равновесным потенциалом при равномерном возрастании потенциала осаждения начнет осаждаться раньше; при этом процесс осаждения второго типа ионов идти не будет. Только после превышения значения равновесного потенциала второго металла будет происходить совместное осаждение ионов двух разных металлов. Подбор соотношения ионов в электролите позволяет минимизировать содержание примеси при большем потенциале. Подбор режимов осаждения и электролитов позволяет получать послойные осадки при резком переключении потенциалов. Однако применение данного метода для получения нанопроволок связано с рядом проблем, таких как определение оптимальных условий осаждения отдельных слоев, отработка методик

9 Ovchinnikova S. N., Poddubnyi N. P., Maslii A. I., Boldyrev V. V., Schwarzacher W., Mutual Influence of

Electrode Processes during Electrodeposition of Layered Structures by the Single-Bath Method: The Effect of Nickel Deposition and Hydrogen Evolution on the Transport of Copper Ions in Acetate and Sulfamate Electrolytes [текст] // Russian Journal of Electrochemistry, V. 38, 2002. pp. 1210-1216

контроля толщин слоев для получения периодичной структуры с сохраняющимися геометрическими и структурными параметрами и т.д10.

В свете изложенного состояния степени проработанности темы, настоящая диссертация посвящена исследованию особенностей заполнения трековых мембран электрохимическим методом для получения нанопроволок из сплавов на основе железа и гетероструктурных нанопроволок для установления зависимостей между режимами получения, структурой и свойствами, что в дальнейшем позволит применять их для создания элементов гибкой микроэлектроники и в качестве компонентов систем для локальной доставки лекарственных средств к очагу заболевания в организме .

Цель и задачи исследования

Целью данной работы является выявление закономерностей формирования, морфологии, кинетики роста и влияния различных факторов на структуру и свойства гомогенных и гетероструктурных нанопроволок заданной геометрии.

Для достижения поставленной цели в работе необходимо было решить следующие задачи:

• разработка способов и отработка режимов получения гомогенных и гетероструктурных нанопроволок с заданным составом и равномерным распределением элементов;

• установление закономерностей формирования, морфологии и кинетики роста нанопроволок сложного состава;

• разработка метода контроля толщины слоев гетероструктурных наноструктур;

• выявление закономерностей изменения физических свойств нанопроволок в зависимости от их геометрии, состава и структуры.

10

Piraux L., George J. M., Despres J. F., Leroy C., Ferain E., Legras R., Giant magnetoresistance in magnetic multilayered nanowires [текст]// Appl. Phys. Lett. 65,1994. P. 2484

Научная новизна диссертационной работы

• Предложен и практически реализован новый способ получения гомогенных наноструктур, состоящих из магнитных сплавов Fe-Ni и Fe-Co, отличающийся возможностью контролируемо регулировать состав сплавов с шагом в 10%;

• Впервые получены экспериментальные данные по кинетике роста наноструктур из Fe-Ni сплавов и предложена на их основе модель роста наноструктур, в соответствии с которой возможно предсказуемо контролировать геометрию наноструктур;

• Впервые установлены закономерности формирования цилиндрических магнитных наночастиц и изменения их структуры в зависимости от режима электроосаждения; при получении наноструктур из сплавов Fe-№ обнаружен эффект аномального (до 35%) осаждения ионов железа в поры матрицы, предложен физический механизм эффекта;

• Выявлены закономерности изменения электрических свойств массивов наночастиц в зависимости от их аспектного соотношения (X), при этом установлено уменьшение на порядок величины (от 106 до 105 Ом) электросопротивления металл-полимерного композита на основе получаемых наночастиц с увеличением X от 20 до 70 единиц;

• Предложен и практически реализован метод контроля толщины (30500 нм) слоев гетероструктурных нанопроволок на этапе роста, отличающийся возможностью получения слоев заданной геометрии вдоль всей длины нанопроволоки;

• Впервые предложен метод получения взвеси калиброванных цилиндрических магнитных наночастиц для локальной доставки лекарств в организме человека, основанный на использовании анизотропных магнитных наночастиц.

• Выявлены закономерности изменения электрокинетического потенциала (дзета-потенциала) взвеси цилиндрических магнитных наночастиц (ЦМНЧ) в зависимости от их аспектного соотношения. При этом установлено, что изменение электрокинетического потенциала обратно пропорционально увеличению аспектного соотношения ЦМНЧ.

Теоретическая значимость работы

Теоретическая значимость диссертации заключается в расширении спектра знаний о процессах получения, формирования, кинетике роста и физических свойствах наноструктур сложного состава; получен массив экспериментальных данных, установлены и проанализированы закономерности исследованных процессов, изменения под действием различных факторов структуры и свойств гомогенных и гетерогенных нанопроволок систем «железо-никель», «железо-кобальт», медь-никель», «медь-кобальт». В результате анализа полученных при исследовании формирования наноструктур экспериментальных данных предложена модель роста наноструктур и показано, что эта модель может использоваться для предсказуемого контроля их геометрии в процессе роста. При получении наноструктур из Fe-Ni сплавов обнаружен эффект аномального электроосаждения ионов железа в поры полимерной матрицы, разработан физический механизм, адекватно объясняющий данное явление.

Практическая значимость работы

Практическая значимость работы заключается в том, что разработанные методики и полученные зависимости позволят в дальнейшем получать одномерные наночастицы и структуры на их основе с заданными структурными, геометрическими параметрами и физическими свойствами.

Разработанные методы позволяют получать массивы НП из магнитных сплавов с заданными составом и структурой, что дает возможность широко варьировать их магнитные свойства. Описанный в работе метод получения взвеси калиброванных цилиндрических магнитных наночастиц позволяет получать наночастицы, которые могут найти свое применение в медицине -для локальной доставки лекарств к очагу заболевания в организме, в качестве компонентов подложек при исследовании гигантского комбинационного рассеивания, устройств магнитного нагрева и т.д. Полученные металл-полимерные композиты могут быть использованы при создании сенсоров, источников электромагнитных волн, а также в качестве элементов гибкой микроэлектроники и спинтроники. Важным обстоятельством, определяющим практическое применение полученных в работе результатов является также то, что используемая матрица производится хорошо освоенным поточным методом, что делает легким процесс масштабирования получаемых объемов наночастиц и наноструктур на их основе.

Научные результаты и публикации

Методология и методы диссертационного исследования

Для получения массивов нанопроволок (НП) в работе использовался метод матричного синтеза, основанный на гальваническом заполнении пор заранее подготовленной матрицы. Выбранная методика позволяет широко варьировать как геометрические, так и структурные параметры получаемых наночастиц. В качестве матриц для создания НП были использованы трековые мембраны производства ОИЯИ, г. Дубна. Матрицы производились путем облучения тонких полимерных пленок из полиэтилентерефталата тяжелыми ионами инертных газов на ускорителе У-400 с последующим растравливанием латентных треков. Облучение производилось с разбросом углов наклона пор до 300 по направлению проката пленки. Это было

необходимо для увеличения плотности облучения с сохранением постоянного диаметра пор. Толщина пленки составляла 12 мкм. Доза облучения составляла 1,2 * 109 см-2. Диаметр пор варьировался за счет процесса растравливания латентных треков и в большинстве работ составлял 100 нм.

Подготовка матрицы до заполнения каким-либо металлом проводилась с использованием ВУП - 4; эта подготовка заключалась в вакуумном термическом нанесении на поверхность матрицы проводящего слоя. На матрицу наносился слой меди толщиной 50 нм. На следующем этапе с помощью источника тока PSM-3004 (GW Instek) напыленый слой гальванически доращивался. Процесс проходил с использованием раствора CuSO4*5H2O и серной кислоты. Катодная плотность тока составляла 7,1 мА/см ; время осаждения составляло 30 мин., что позволяло дорастить напыленный слой до толщины в 4 мкм. Данный слой полностью перекрывал поры матрицы и являлся катодом для проведения электрохимического осаждения в поры матрицы.

Для синтеза нанопроволок в работе применялся метод гальванического осаждения в поры трековых мембран. Процесс проводился в специальной гальванической ячейке, в которой анод и матрица располагались вертикально. Площадь образца трековой мембраны, в которую проводилось осаждение, составляла 1,8 см ; таким образом, площадь рабочего электрода (поверхностная площадь пор матрицы) составляла 0,17 см2. В качестве источника применялся потенциостат - гальваностат ЕНш Р-2Х. Потенциалы осаждения изменялись в пределах от 0,5 до 2 В. Процесс проводился по двухэлектродной схеме.

Для осаждения НП из сплавов Fe-Ni применялись электролиты следующего состава: NiSO4 * 7Н20 - 16 г/л; №С12 * 6Н20 - 40 г/л и FeSO4 *7Н20, концентрация которого изменялась от 4 г/л до 32 г/л с шагом в 4 г/л.

Для создания НП из сплавов FeCo электролиты содержали CoSO4 * 7Н20 - 16 г/л; СоС12 * 6Н20 - 40 г/л. Концентрация FeSO4 *7Н20 при этом изменялась от 4 г/л до 72 г/л, что соответствовало изменению соотношения ионов железа и кобальта от 6% до 53%. Для большего увеличения относительной концентрации ионов железа концентрация солей кобальта снижалась в следующей последовательности - CoSO4 * 7Н20 - 12 г/л, 8 г/л, 4 г/л, 2 г/л, 2 г/л; СоС12 * 6Н20 - 32 г/л, 24 г/л, 16 г/л, 8 г/л, 4 г/л. Этот приём позволил изменять относительную концентрацию ионов железа от 59% до 91%. Во всех случаях применялись добавки: борная кислота Н3В03 - 25 г/л, лаурилсульфат натрия - 1 г/л (для увеличения смачиваемости пор матрицы) и аскорбиновая кислота - 1 г/л (для предотвращения перехода двухвалентных ионов железа в трехвалентное состояние).

Для создания слоевых НП применялся электролит следующего состава: NiSO4*7H2O - 196,7 г/л; С^04*5Н20 - 6,25 г/л; Н3В03 - 31,6 г/л.

Для получения взвеси цилиндрических магнитных наночастиц (ЦМНЧ) образцы слоевых НП помещались в раствор №Н4ОН на 72 часа для селективного удаления медных прослоек. После растворения меди ЦМНЧ выделялись из раствора магнитом.

Для выполнения структурных исследований применялся комплекс из нескольких приборов для проведения растровой, просвечивающей электронной микроскопии с приставками для элементного анализа, рентгеноструктурного анализа.

Исследования морфологии получаемых нанообъектов, их состава и скорости роста проводили методом растровой электронной микроскопии (РЭМ), при этом использовался растровый электронный микроскоп JEOL JCM-6000plus, оснащенный приставкой для элементного анализа. Следует отметить, что для проведения РЭМ-исследования матрица удалялась в растворе №аОН.

Рентгеноструктурные исследования проводились на порошковом рентгеновском дифрактометре MiniFlex-600.

Важно отметить, что характеристическими параметрами наночастиц, являются материал частицы, ее размеры, а также электрокинетический потенциал (дзета-потенциал). Дзета-потенциал возникает в результате накопления электрических зарядов на границе раздела твердой и жидкой фаз, в результате этого на фазовой границе образуется двойной электрический слой. Дзета-потенциал определяет степень и характер взаимодействия между частицами дисперсной системы. Для молекул и частиц, которые достаточно малы, высокий дзета-потенциал будет означать стабильность, т.е. устойчивость по отношению к агрегации (коагуляции) частиц. Когда дзета-потенциал низкий, притяжение превышает отталкивание, и устойчивость дисперсии будет нарушаться. Коллоиды с высоким дзета-потенциалом являются электрически стабилизированными, в то время, как коллоиды с низким дзета-потенциалом склонны коагулировать. Измерение электрокинетического потенциала (дзета-потенциала) проводилось в работе с помощью автоматического анализатора Zetasizer Nano ZS (Malvern, Великобритания).

Совокупность данных, полученных с использованием вышеописанных методов, позволила сделать выводы о характере получаемых структур, их составе, кинетике роста массива, структуре и диффузионным процессам в порах с привязкой к режимам осаждения.

Основные положения, выносимые на защиту:

- новый способ получения гомогенных наноструктур, состоящих из магнитных сплавов Fe-Ni и Fe-Co;

- экспериментальные данные по кинетике роста наноструктур из Fe-Ni сплавов и предложенная на их основе модель роста наноструктур;

- закономерности формирования цилиндрических магнитных наночастиц и изменения их структуры в зависимости от режима электроосаждения; обнаруженный при получении наноструктур из сплавов Fe-Ni эффект аномального (до 35%) осаждения ионов железа в поры матрицы, физический механизм эффекта;

- закономерности изменения электрических свойств массивов наночастиц в зависимости от их аспектного соотношения;

- новый метод контроля толщины (30-500 нм) слоев гетероструктурных нанопроволок на этапе роста;

- новый метод получения взвеси калиброванных цилиндрических магнитных наночастиц для локальной доставки лекарств в организме человека;

Достоверность полученных результатов

Достоверность экспериментальных результатов, представленных в диссертационной работе, подтверждается их воспроизводимостью, а также использованием современного экспериментального оборудования, независимых методов исследования: просвечивающей электронной микроскопии, растровой электронной микроскопии, просвечивающей растровой электронной микроскопии, электронной дифракции, энергодисперсионного анализа, рентгеноструктурного анализа. Интерпретация полученных данных базируется на современных представлениях о процессах формирования и механизмах роста нанопроволок. Разработанное технические решение способа получения нанопроволок никеля было запатентовано: выдан патент РФ на изобретение.

Личный вклад автора

Личный вклад автора в работу состоит в исследовании процессов получения нанопроволок и структур на их основе, разработке модели роста

исследуемых наноструктур, исследовании их морфологии, структуры, элементного состава методами растровой электронной микроскопии с приставкой для элементного анализа и рентгеноструктурного анализа включая пробоподготовку; разработке режимов электроосаждения для получения слоевых нанопровлок с регулируемой и постоянной толщиной слоев, а также методик для селективного травления гетероструктурных нанопроволок для получения взвеси калиброванных магнитных наночастиц; участии в подготовке и проведении исследований магнитных и электрических свойств массивов получаемых нанопроволок, взвеси наночастиц и структур на их основе; проведении анализа полученных результатов; формулировке выводов по диссертационной работе.

Апробация результатов

Основные результаты диссертации были представлены на следующих всероссийских и международных конференциях:

1. 2017 Materials Research Society Spring Meeting and Exhibit. Доклад «Fabrication of aligned carbon nanotubes and magnetic nanowires using porous polymer template», США, Феникс, 2017, 17 - 21 апреля.

2. Magnetism 2019. Доклад «Template synthesis and magnetic properties of two-component nanowires», Великобритания, Лидс, 2019, 8-9 апреля.

3. E-MRS 2019 Fall Meeting, 2019. Доклад « Nanowires of FeNi and FeCo alloys: matrix synthesis and structure», Польша, Варшава, 2019, 16 - 19 сентября.

4. International Conference on Materials for Energy Applications (ICME-18). Доклад «Template synthesis of heterostructural nanowires Cu/Ni», Индия, Джайпур, 2018, 6 - 8 декабря.

5. The 9th International Conference on Physical and Numerical Simulation of Materials Processing (ICPNS'2019). Доклад «Characterization of nanowires of FeNi and FeCo alloys», Россия, Москва, 2019, 10-14 октября.

6. International Baltic Conference on Magnetism 2021. Доклад «FeNi and FeCo alloys nanowires: synthesis, structure and magnetic properties», Россия, Светлогорск, 2021, 29 августа - 2 сентября.

7. Международная конференция по нанофизике и наноэлектронике 2018. Доклад «Получение слоевых нанопроволок, исследование их структуры и магнитных свойств». Россия, Нижний Новгород, 2018, 12 - 15 марта.

8. Международная конференция по нанофизике и наноэлектронике 2019. Доклад «Структура многослойных нанопроволок с чередованием магнитного и немагнитного металлов». Россия, Нижний Новгород, 2019, 11 - 14 марта.

9. Международная конференция по нанофизике и наноэлектронике 2020, Нижний Новгород, Россия. Доклад «Нанопроволоки FeNi и FeCo: синтез, структура и Мёссбауровские спектры». Россия, Нижний Новгород, 2020, 10 -13 марта

10. XXVII Международная конференция «Радиационная физика твёрдого тела». Доклад «Применение трековых матриц для получения гетероструктурных нанопроволок Ni/Cu». Россия, Севастополь, 2017, 10 - 15 июля.

11. ХХУШ Международная конференция «Радиационная физика твёрдого тела». Доклад «Применение ядерных фильтров для получения слоевых нанопроволок». Россия, Севастополь, 2018, 9 - 14 июля.

12. XXIX Международная конференция «Радиационная физика твёрдого тела». Доклад «Электро-химическое заполнение ядерных фильтров (трековых мембран) для получения нанопроволок переменного состава». Россия, Севастополь, 2019, 8 - 13 июля.

13. XXX Международная конференция «Радиационная физика твёрдого тела». Доклад ««Матричный синтез и исследование нанопроволок из сплава FeNi». Россия, Севастополь, 2020, 7 - 12 июля.

Список опубликованных статей по теме диссертации

Основные положения по теме диссертации изложены в 6 публикациях, проиндексированных в международной системе Scopus:

1. Structure of Cu/Ni Nanowires Obtained by Matrix Synthesis // O. M. Zhigalina, I. M. Doludenko, D. N. Khmelenin, D. L. Zagorskiy, S. A. Bedin,I. M. Ivanov / Crystallography Reports, 2018, Vol. 63, No. 3, pp. 480-484. DOI: 10.1134/S1063774518030379 (Q3);

2. Structure and Magnetic Properties of Nanowires of Iron Group Metals Produced by Matrix Synthesis // Zagorskiy D.L. ; Frolov K. V.; Bedin S. A.;

Perunov I. V.; Chuev M. A.; Lomov A. A.; Doludenko I. M. / Physics of the solid state. Vol. 60, No. 11 pp. 2115-2126 (2018) DOI: 10.1088/17426596/1134/1/012071 (Q3);

3. Specific Features of Obtaining of Metal Nanowires by Replication of Pores of Track Etched Membranes // D. Zagorskiy, I. Doludenko, A. Shatalov/ Key Engineering Materials, 2018, Vol. 781, pp. 170-175. (DOI: https://doi.org/10.4028/www.scientific.net/KEM.781.170) IF: 0.39 (Q3);

4. Fabrication of Cylindrical Magnetic Nanoparticles for Functionalization of Polyelectrolyte Microcapsules // I. M. Doludenko, A. V. Mikheev, I. A. Burmistrov, D. B. Trushina, T. N. Borodina, T. V. Bukreeva, D. L. Zagorskii / Technical Physics, 2020, Vol. 65, No. 9, pp. 1377-1383. DOI: 10.1134/S1063784220090121 (Q3);

5. I. M. Doludenko. Aspects of Pore Filling in Synthesis of FeNi Alloy Nanowires Using Track-Etched Membranes / I.M. Doludenko // Inorganic Materials: Applied Research, 2022, Vol.13, No.2, pp. 531-535 DOI: 10.1134/S2075113322020125 (Q2);

6. I.M. Doludenko, I.S. Volchkov, B.A. Turenko, I.O. Koshelev, P.L. Podkur, D.L. Zagorskiy, V.M. Kanevskii, Electrical properties arrays of intersecting of nanowires obtained in the pores of track membranes, Materials Chemistry and Physics (2022), doi: https: //doi .org/ 10.1016/j matchemphys .2022.126285(Q2).

Список литературы диссертационного исследования кандидат наук Долуденко Илья Михайлович, 2023 год

- 1.0 V

—"y FeNi 1.2 V "

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Fig. 12. Hysteresis loops for: (a) iron—cobalt samples; (b) for FeCo samples.

tions of the external magnetic field attracts attention. In a common case of domains with axial magnetic anisotropy, the hysteresis loop width is expected to be maximal when the field is oriented along a "light," i.e., NW, axis, while the magnetization curve is almost paramagnetic (loop-free) for perpendicular orientation. It is worth mentioning that the loop is quite narrow for a sample with a NW diameter of 200 nm, where the magnetic properties are close to those of the conventional magnetosoft material.

The measured data for nonoriented iron-cobalt and iron—nickel samples are shown in Fig. 12.

For FeCo samples, the coercive force and remaint magnetization are calculated to be respectively 630 and 1100 Oe and 27 and 18 memu; i.e., these samples are magnetohard. Unlike iron-cobalt systems, the coercive force and remain polarization for FeNi samples are found to be 75, 80, and 140 Oe and 1, 1.3, and 2.2 memu; i.e., the latter are attributed to magnetosoft materials.

As observed for both series of samples, the higher is the growth voltage, the greater are the magnetohard characteristics; i.e., there is a rise in coercive force and remaint magnetization. This can be assumed to be due to the fact that increasing the growth rate leads to the formation of fine-grained structure (as is indirectly evidenced by XRD data).

The hysteresis loops for iron—nickel samples (with NWs of different diameters and orientations) are plotted in Fig. 13. One observes a typical orientation

dependence, i.e., for a field co-directed with the NW axis (zero inclination), a hysteresis loop is much broader than for a field making a 90° angle with a NW axis. Notice that the nickel alloy for NWs with small diameters behaves itself as the magnetohard materials.

3.5. Mossbauer Spectroscopy

The Mossbauer spectra for all NW array samples evidence the characteristic magnetic splitting and are composed of weakly broadened sextets (Figs. 14—16). The greater broadening of spectra of Co—Fe and Ni— Fe NWs seems to be a result of the distribution of hyperfine interaction parameters because of the forming several positions of iron ions in the bcc lattice of a cobalt or nickel matrix [16].

The spectra of pure iron NW arrays obtained at various deposition potentials have similar hyperfine parameters to the bulk materials. However, at potentials above the absolute value of 800 mV, the Mossbauer spectra reveal the presence of low-intensity paramagnetic doublets from the appropriate iron ions in Fe-Cu alloys, which form at the onset of deposition on a copper substrate [20]. Besides this, the intensities /, of lines / of a Mossbauer sextet (/, 6: /2 5: /3 4) in a sample obtained at a potential of -750 mV are found to be different from a value of 3 :2 : 1, which is characteristic of the randomly oriented magnetic moments in polycrystalline bulk samples.

PHYSICS OF THE SOLID STATE Vol.60 No. 11 2018

Fig. 15. Mossbauer spectra ofFe—Co NW arrays with NW diameters of 50, 100, and 200 nm (the growth voltage was 750 mV).

V, mm/s

Fig. 16. Mossbauer spectra of Fe—Ni NW arrays.

The spectra of iron—cobalt NW arrays (with different diameters) are shown in Fig. 15.

It is obvious that only the NWs with diameters of 200 nm give a sextet with the classical intensity ratio of 3:2:1, typical of bulk nonoriented alpha-iron. The change in the arbitrary intensities of the second and fifth lines in spectra of NWs with smaller diameters

PHYSICS OF THE SOLID STATE Vol.60 No. 11 2018

evidences the presence of the preferred direction of magnetization.

The Mossbauer spectra of Fe—Ni NWs are shown in Fig. 16.

As follows from the Mossbauer spectroscopy data, the FeCo alloy may be composed of three phases, while FeNi exhibits two phases. The metal deposition in pores with greater diameters as well as the deposition at low rates results in NWs whose properties are close to the bulk materials. It is worth mentioning that, unlike the earlier studied pure iron NWs where spontaneous magnetization arises at certain conditions, all the alloy samples in the present work exhibit magnetization. The field at 57Fe cores in FeCo NWs is about 3 T greater than for pure iron NWs, whereas that for FeNi alloy is 5 T less than for pure iron NWs.

4. CONCLUSIONS

The growth matrix parameters and growth conditions were found to exert influence on all the characteristics of NW arrays. Varying the growth makes greater contribution than the change in pore channel diameters. As established for all samples, the lower was the growth rate (i.e., at the minimum growth voltage), the closer were the properties of NWs to the bulk materials, as was also observed with increasing the pore diameters. NWs with diameters of 200 nm exhibited predominately the properties of the bulk material. The element composition of the binary NW arrays (alloys) was different from that of electrolyte, first of all, by the relatively increased iron concentration, depending on the synthesis conditions. Furthermore, the NW composition varied with length.

The fundamental ability to tune the magnetic properties of nanowires upon their synthesis by varying the composition of the electrolyte, the deposition rate and the pore diameter was thereby shown. However, the production of nanowires with predetermined magnetic properties still necessitates a large amount of complementary experiments, i.e., with involving the external magnetic fields.

ACKNOWLEDGMENTS

This work was supported by the Federal Agency of Scientific Organizations within the framework of the state task (agreements nos. 007-GZ/Ch3363/26 and 007-GZ/Ch 1824/66). The Mossbauer spectroscopy measurements were partially supported by the Russian Science Foundation (project no. 14-12-00848).

The authors are grateful to P.Yu. Apel' (Joint Institute of Nuclear Research, Dubna) for provision of polymer matrices, V.V. Korotkov (Russian Chemico-technical University, Moscow) for production of iron—cobalt samples and to V.V. Artemov and D. Khmelenin (Federal Research Center "Crystallography and Photonics") for help with electron micros-

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copy measurements, and to S.N. Sul'yanov (National Research Center "Kurchatov Institute") for organization of X-ray diffraction experiments. This work was also partially performed using the facilities of the Centre of Collective Usage (Institute of Crystallography, Russian Academy of Sciences).

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Translated by O. Ma s I ova

PHYSICS OF THE SOLID STATE Vol. 60 No. 11 2018

Приложение 3: статья «Specific features of obtaining of metal nanowires by replication of pores of track etched membranes»

Key Engineering Materials ISSN: 1662-9795, Vol. 781, pp 170-175 doi: 10.4028/www.scientific.net/KEM.781.170

© 2018 Trans Tech Publications, Switzerland

Key Engineering Materials ISSN: 1662-9795, Vol. 781, pp 170-175 doi:10.4028/inn v. scientific. net/KEM. 781.170 © 2018 Trans Tech Publications, Switzerland

Submitted: 2018-06-14 Accepted: 2018-06-19 Online: 2018-09-28

Specific Features of Obtaining of Metal Nanowires by Replication of Pores of Track Etched Membranes

Dmitri Zagorskiy1,2'3*, llya Doludenko1'3,6 and Aleksander Shatalov1,3,0

1FSRC "Crystallography and Photonics" of Russian Academy of Sciences, 59, Leninsky Ave.,

Moscow, 119333, Russia

2Gubkin Russian State University of Oil and Gas, 65-1, Leninsky Ave., Moscow, 119991, Russia

3National Research University Higher School of Economics, 20, Myasnitskaya St., Moscow,

101000, Russia

a*[e-mail], [e-mail], [e-mail]

Keywords: track etched membranes, matrix synthesis, electrodeposition, nanowires, effect of magnetic field.

Abstract. Ensembles (massives) of metal nanowires (with diameters 50-200 nm) were obtained using method of template synthesis. Polymer track etched matrixes were used as template. Nanowires obtained were the replicas of the pores in these membranes. The problems of choosing of electrolyte and different regimes of electrodeposition were discussed. Different techniques of separation of obtained nanowires from growth polymer matrix were used- etching at elevated temperature, ultrasound and UV-treatment. The regimes of obtaining of layer Cu/Ni nanowires were investigated and the optimal voltages were found: 0.8 V for Cu-layer and 1.8 for Ni layer. It was also found that application of magnetic field accelerate the process of electrodeposition; moreover, application of SOUTH pole leads to formation of hollow Ni-layers. Using of "two-bath" method of electrodeposition found to be optimal for obtaining of two-parts wires. Such wires could be used for generation of THz irradiation.

Introduction

One of the promising applications of radiation technologies is the production of special matrices for template synthesis, for obtaining arrays of a special type of nanoobjects-nanowires. In this paper, we consider some features of the use of track matrices in this process.

In general, the production of nanomaterials is one of the key areas of science and technology. Among the many different types of nanomaterials, one-dimensional nanowires (nanorods) are of particular interest. One of the promising methods of obtaining such objects is the method of matrix (template) synthesis. The basic idea of the approach consists in a two-stage synthesis. At the first stage a special porous matrix with a big number of identical nano-sized pores is made. The pores in such a matrix are then filled with the required material, which forms the replicas of the pore channels. This method allows to obtain the arrays (ensembles) from a large number (up to 1010 per cm2) of nanowires (NWs), identical in geometry - diameter and length. Note that various materials, porous silicates, porous alumina, polymeric track membranes can be used as a matrix. Materials "loaded" in the pores, can also be very different - semiconductors, polymers, water-soluble crystals, metals. The type of material determines the "loading" method, which can be very different, from mechanical to chemical and electrochemical.

The idea of obtaining the pores replicas was first realized in [1], where the author galvanicaly deposited the tin into the pores of mica. The paper [2] describes how cobalt and nickel were successfully deposited in a porous oxide matrix; there it was suggested to use such structures in magnetic recording devices. In subsequent works, the electrodeposition of the metals was carried out already in the track pores of polymer matrices [3-5]. The basic ideas of the method of matrix synthesis are described in detail in the famous review by Martin [6]. In subsequent years, many researchers worked out methods for obtaining replicas of pore channels and the synthesis of NWs from various metals.

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In the present work, polymeric track membranes were used as the matrix, in the pores of which NWs from metals - primarily metals of the iron group (cobalt, nickel and iron) were deposited by electrochemical (galvanic) method.

It should be noted that electrochemical deposition is one of the oldest and proven technological processes. Its undoubted advantage is the ability to regulate the main parameters of the process within a wide range and the high repeatability of the results in a classical process. This process was successfully implemented when the metal was filled into the pores of track membranes at the end of the last century [7, 8]. Despite the fact that a large number of works were subsequently published, practically no attention was paid to the methodological aspects of obtaining nanowires. In many cases, the details of the process were simply not described by the authors. Because of this, there are many difficulties in comparing of the results obtained by different authors and poor reproducibility of the results.

In this paper, we consider a number of methodological features of several main stages of obtaining NP arrays: the stage of obtaining the matrix, the stage of choosing the electrolyte, the actual galvanic process, and finally, the separation of the synthesized massive of NWs from the growth polymer matrix.

Experimental

The Matrix. Polymer track membranes are traditionally used as matrices. The latter are obtained by irradiation of the polymer film with accelerated heavy ions (at this stage, the so-called latent tracks are formed) and subsequent etching in an alkaline solution (while latent tracks are converted into through pores). The production of track membranes is a semi-industrial process now. It should be noted here that usually track membranes are made for the needs of fine filtration, for which the pore density should be maximal, and the pores themselves are not parallel (they usually have a wide spread in directions to reduce the probability of crossing). Matrix synthesis, as a rule, requires membrane-matrices with parallel pore channels and (as a rule) with a relatively low pore density. Thus, industrial track membranes are not always optimal and for the synthesis of nanowires it is necessary to manufacture special matrices. Such matrices are made of a polymer film irradiated in a special way: irradiation is carried out strictly perpendicular to the surface and with a relatively small dose of 106 -107 ions per square cm. In some cases, the subsequent obtaining of the through-pores is not required, and the "dead-end" pores are used. Thus, the materials obtained are no longer strictly speaking membranes - it is more correct to call them track matrices.

The material of track membranes in Russia is traditionally polyethylene terephthalate (PET), while polycarbonate (PC) is more often used in the West. These polymers are similar in structure and type of chemical treatment, but there are some differences. So, after etching of the irradiated PC formed pores have smoother walls than in PET. We note that for filtration process the first option is more desirable, while in order to obtain magnetic structures the "nonsmooth" walls are preferred.

Electrolytes. Electrolyte selection is the key point of matrix synthesis. A lot of articles and reviews are devoted to this question, of which it can be noted - [9].

Here only a few points could be mentioned. The basis of the electrolyte is the salt (of the metal that needs to be precipitated). Most often, sulfate salts are used, one of the advantages of which is their good solubility. In the case of a multicomponent composition mixture of salts is used. In addition to salts, acids can be added to the electrolyte (for increasing the electrical conductivity of the solution), buffer additives (to maintain the necessary acidity). Ascorbic acid and lauryl sulfate are also used. The composition of electrolytes can vary greatly depending on the solution The choice of the electrolyte and the choice of the deposition regime may depend on the choice of the anode. It is possible to use an insoluble anode (for example, coal anode) - however, there arises the problem of changing the composition of the electrolyte-enhancing it by the ions of the metal being deposited. Most often the anode used is made of the same metal that is deposited during the synthesis, while dissolving the anode compensates for the loss of metal ions due to electrodeposition. However, in this case, there is a risk contamination of the solution with

impurities frequently present in the anode, and the problem of compensation for outgoing ions is not solved in this case when depositing a multicomponent (two-component) material.

The process of electrodeposition is carried out in a special galvanic cell. Often, the electrolyte is stirred to accelerate the diffusion process in the cell and to remove gas bubbles formed at the "mouths" of the pores and blocking the ion transport. The process itself can be carried out in different modes - usually galvanostatic (at constant current) and potentiostatic (at a constant potential). The latter mode is used more often: during the process in this case, the current versus time is recorded - the potentiostatic curve. The latter allows monitoring of the process and displays various stages of electrodeposition. Thus, the onset of a sharp increase in current usually means that the pore channel is completely filled and the growth of the metal outside the matrix begins, usually the process should be stopped at this time or earlier.

Separation of the Growth Matrix. The resultant polymer matrix with inserted metal filaments-nanowires is a kind of metal-polymer composite. This composite can be investigated and used in a number of applications. However, in most cases, the polymer matrix must be removed, releasing the formed "array" (ensemble) of free-standing NWs. Typically, the polymer is removed by dissolving in concentrated alkali at the high temperature. Often, after removal of the polymer matrix, polymer fragments still remain between thin NWs, especially in the case of NWs with small diameters and high surface densities. In this case, sometimes ultrasound treatment is used- during etching or after it. But after these processes of "hard" removing of matrix, the resulting wires can be damaged. To "soften" the process, there is a preliminary "embrittlement" of the polymer: it is treated with UV irradiation (X = 320 nm, 24 hours), after which the polymer is removed much more easily. We also developed the method of pre-etching of the matrix, after which it can be removed mechanically.

Obtaining of Layer Cu/Ni Nanowires. It is known that it is possible to obtain heterogeneous layer NWs (structures from alternating layers of different metals) by changing the deposition potential. Thus, during electrodeposition from an electrolyte containing ions of two metals initially (at a low voltage), a metal with a lower equilibrium deposition potential will precipitate, then (with increasing voltage) a metal with a higher equilibrium potential will be deposited. In the latter case, an "alloy" of two metals will form; the ratio of the components in such alloy can be varied by changing the concentration ratio in the electrolyte.

In this paper, the deposition regimes of Cu / Ni layer structures were determined. For this purpose an electrolyte of the following composition was used: NiS04 • 7H20 - 200 g /1; CuS04 • 5H20 - 6 g /1; H3BO3 - 30 g /1. First, the deposition was carried out on a flat surface. A series of samples was obtained, with the potential varying stepwise from 0.2 V to 3 V (with 0.2 V steps). After preparation, the samples were examined on a scanning electron microscope with elemental analysis. Figure 1 shows the dependences of the atomic concentration of nickel and copper for samples with different deposition potentials.

120

100

80

60

U 40

20 0

0.2 0.6 1 1.4 1.8 2.2 2.6 3

U, B

Figure 1. Graphs of the dependence of the composition of the sample on the growth voltage.

It can be seen that at a potential up to 0.8 V the nickel concentration is zero, then starting from 1 V it rises sharply and at a potential of 1.8 V goes to the "plateau" (nickel concentration: 80-^83%). At the same time, the concentration of copper after 0.8 V sharply decreases. Thus, it can be concluded that the optimal potential for copper deposition is 0.8 V, and for deposition of nickel-1.8 V. According to microscopic data, deposition at these potentials gives a good surface quality. Note that with the growth of the potential the ratio of the elements does not change, only a slight acceleration of the process took place, but the surface becomes much more loose -t.e. increasing the potential is undesirable. The obtained parameters were then successfully used for the growth of NWs arrays of Cu/Ni layer structures.

Influence of Magnetic Field. Of great interest are the problems of direct influence on the growth of nanowires during the electrodeposition. As one of the possibilities it is application of the magnetic field. The effect of the magnetic field during the growth of the NWs array was studied for the above-mentioned ensembles of the Cu / Ni layer structures, as well as for the NiFe (Ni-50%, Fe-50%) alloy. During electrodeposition, a permanent magnet was attached to the growth matrix from the back side. We used a neodymium magnet with a magnetic induction of 0.25 T, which was applied sequentially both by the south and north pole. The deposition curves obtained for both types of samples, for two directions of the magnetic field, and for control samples grown without application of the field, are presented in Figure 2.

.North pole South pole Control

North pole

Control

0.025

0

150

300

450

600

t, c

Figure 2. Graph of current versus time for growth for various orientations of the external magnetic field: a - growth of layer structures (fragment of the graph is the "top" of one peak for different orientation of external field and without field-Control), b - growth of alloys.

It can be seen that the magnetic field has a significant effect on the deposition process: the application of the field accelerates the process, and with the application of the northern pole the growth rate is higher (for both cases- deposition of alloy and layered structure). Preliminary X-ray examinations of the obtained NWs alloy were carried out. It is shown that the application of a magnetic field during the growth of an alloy leads to a change in the ratio of the X-ray lines intensity. So, the appearance of the texture could be supposed. The resulting arrays were then separated from the growth matrix and studied with the electron microscope. These studies have shown that the magnetic field has practically no effect on the shape of the alloy NWs. At the same time, a strong influence on the topography of layer NPs was found. Thus, at the tops of the NWs

grown at the application of the south pole, hollows (cavities) were found, and the NWs in this part has the shape of a "tube". This part of the NWs corresponds to the nickel layer, which grew at a greater potential. Proceeding from this, it can be assumed that all layers of nickel are also hollow inside and "sealed" by the layers of copper then deposited, thus forming a kind of capsule. In the sample of NWs, to which a south pole magnet was applied during growth, no formation of cavities was observed. However, the length of the NWs in this case increases noticeably comparison with a sample grown without applying a magnetic field. This is due to the increase of curren during the growth of the array.

"Two - Bath" Deposition. The samples of NWs, consisting of only two layers, were also obtained in this work. For this case, two methods of forming layer structures were compared: "Single-bath" and "double-bath". In the first of these, described above, the process was carried out "in one bath" - in one electrolyte containing ions of two metals. In the second case, the growth of wo metals is carried out sequentially in two different electrolytes with different ions ("in two baths"). The second method is now practically not used for the preparation of layer NWs because of possible problems associated with the change of electrolyte and the resulting plugging of individual pores. However, a comparison of the results obtained in the work showed that the "two-bar" method produced better results, in particular, because of the possibility of obtaining "clean layers" (without the admixture of the second metal). Moreover, this approach gave possibility of sequential separate deposition of metals with close deposition potentials- such as Ni and Co. Thus, this method (which historically was the first in the production of multilayer coatings on a flat surface) showed its advantage, at least with the growth of NPs consisting of two layers (two parts) and, accordingly, requiring only one change of electrolyte. Note that structures consisting of two layers, for example, including contact of metals with different magnetic properties, now attract a lot of attention. Thus, in our work [10], the possibility of generating terahertz radiation was shown when a high-density current was flow through such a structure.

Summary

The paper shows the possibilities of the matrix synthesis method for obtaining of nanowires of different types, including layer structures. External magnetic field was shown to be effective to vary the NWs parameters.

Acknowledgments

This work was supported by the Federal Agency of Scientific Organizations (Agreement No 007-r3AI 3363/26). The authors thank Prof. P.Ya. Apel (JINR, Dubna) for track membranes, Senior Res. Inst of Crystallography V.V. Artemov for SEM investigation, MSU student S.Chechumyan for X-ray research.

References

[1] G.E. Possin, A method of forming of very small diameter wires, Rev. Sci. Instrum. 41(5) (1970)772-774.

[2] S. Kawai, R.J. Ueda, Magnetic Properties of Anodic Oxide Coatings on Aluminum Containing Electrodeposited Co and Co-Ni, J. Electrochem. Soc. 112 (1975) 32-36.

[3] S.K. Chakarvarti, J. Vetter, Morphology of etched pores and microstructures fabricated from nuclear track filters, Nucl. Instr. Meth. Phys. Res. 62(1) (1991) 109-115.

[4] J. Vetter, R. Spolir, Application of ion track membranes for preparation of metallic microstructures, Nucl. Instr. Meth. Phys. Res.79(l-4) (1993) 691-694.

[5] T.M. Whitney, J.S. Jiang, P.C. Searson, C.L. Chien, Fabrication and Magnetic Properties of Arrays of Metallic Nanowires Science 261(5126) (1993) 1316-1319.

[6] C.R. Martin, Nanomaterials: A membrane based synthetic approach, Science 266(5193) (1994)1961-1966.

[7] N. Lupu (ed.), Electrodeposited nanowires and Their Applications, InTech, Croatia, 2010.

[8] M. Va'zquez (ed.), Magnetic Nano- and Microwires: Design, Synthesis, Properties and Applications, Woodhead Publishing, Elsevier, 2015.

[9] A.A. Davydov, V.M. Volgin, Template Electrodeposition of Metals, Electrochemistry 52(9) (2016) 905-933 (in Russian).

[10] S.G. Chigarev, E.A. Vilkov, G.M. Mikhailov, A.V. Chernykh, D.L. Zagorsky, S.A. Bedin, I.M. Doludenko, A.S. Shatalov, Spin-inject Generators of THz-irradiation based on nanostructures, In: Proc. of V All-Russian Microwave Conference, Moscow, Russia (2017) 195-197 (in Russian).

Приложение 4: статья «Fabrication of Cylindrical Magnetic Nanoparticles for Functionalization of Polyelectrolyte Microcapsules»

ISSN 1063-7842, Technical Physics, 2020, Vol. 65, No. 9, pp. 1377-1383. © Pleiades Publishing, Ltd., 2020.Russian Text © The Author(s), 2020, published in Zhurnal Tekhnicheskoi Fiziki, 2020, Vol. 90, No. 9, pp. 1435-1441

ISSN 1063-7842, Technical Physics, 2020, Vol. 65, No. 9, pp. 1377-1383. © Pleiades Publishing. Ltd.. 2020. Russian Text © The Authorfs). 2020. published in Zhurnal Tekhnicheskoi FizJki, 2020, Vol. 90, No. 9, pp. 1435-1441.

_ NANOMATERIALS IN BIOLOGY _ AND MEDICINE

Fabrication of Cylindrical Magnetic Nanoparticles for Functionalization of Polyelectrolyte Microcapsules

I. M. Doludenko" *, A. V. Mikheev" \ I. A. BurmistroV7, D. B. Trushina"c, T. N. Borodina"c, T. V. Bukreeva"</, and D. L. Zagorsk»"

a Federal Research Center Crystallography and Photonics, Russian Academy of Sciences, Moscow, 119333 Russia b Moscow State University, Moscow, 119991 Russia c Sechenov First Moscow State Medical University, Moscow, 119991 Russia d National Research Center Kurchatov Institute, Moscow, 123098 Russia * e-mail: [e-mail] Received December 16, 2019; revised December 16, 2019; accepted February 17, 2020

Abstract—A problem of fabrication of magnetic polymer capsules for targeted drug delivery is considered. Magnetic nanoparticles are used in the problem under study. A method for fabrication of such particles involving synthesis of layered nanowires with alternating layers of the specified magnetic metal and sacrificial layers of nonmagnetic metal is proposed. A method for template-assisted synthesis based on ac-potential electroplating of specified metals in the pores of track membranes is used to fabricate wires with a diameter of 100 nm with nickel layers of 400 and 200 nm. A method for the subsequent extraction of nickel fragments using selective etching (removal) of copper fragments is developed. Procedures that prevent aggregation of magnetic nanoparticles and penetration of the nanoparticles in the shells of polymer capsules are considered.

DOI: 10.1134/S10 63784220090121

INTRODUCTION

It is known that magnetic particles are widely employed in biology and medicine. Targeted drug delivery is among topical problems under study. For efficient treatment, a drug must be delivered to organism at a specified location and be activated therein. (Relatively high doses are needed when the organism is affected as a whole, and side effects are probable.) A method to solve such a problem can be based on encapsulation, which employs deposition of a drug to a capsule that is used for targeted delivery. The corresponding works were actively performed over the last 10-15 years.

Successful applications of polymer multilayer capsules for drug delivery and procedure for controlled release can be found in [ 1 ]. Analysis of several methods for fabrication of capsules, delivery of drug molecules into the capsules and to the capsule shells, and possible methods for functionalization have been presented in [2]. Application of polyelectrolyte and nano-composite microcapsules (fabricated with the aid of layer deposition) for encapsulation and drug delivery for diagnostic purposes has been reviewed in [3]. Several methods to improve the functional properties of capsules (e.g., ultrasound, external magnetic fields (MFs), and laser and short-wavelength irradiation) have been considered. It has been mentioned that

short-term ultrasonic or IR irradiation can be used for opening of capsules.

A method for functionalization of capsules can be based on introduction of magnetic particles into the capsules. In this case, delivery of capsules to the desired location can be performed with the aid of MF. (Note that such an approach does not solve several problem: in particular, the propagation of capsules is primarily determined by the blood flow, so that field correction can be difficult to implement. The method is efficient for vessels with relatively low blood flow.) The method has been studied in several works. In particular, polyelectrolyte capsules have been modified for magnetic delivery using electrostatic adsorption of preliminary synthesized magnetite nanoparticles on the charged part of the shell [4]. In an alternative approach of [5-7], magnetic nanoparticles have been synthesized directly on the capsule shell.

Magnetic particles introduced in a polymer capsule can be used to solve the problem of local heating. Such a problem emerges when targeted thermal action on a diseased organ (or cells of certain type, for example, cancer cells) is required.

The problem is solved using effect of ac MF on capsules with magnetic particles that were preliminary delivered to the required location. MF with a certain frequency leads to heating of such particles due to conversion of field energy into thermal energy. Note that

1377

1378 DOLUDENKO et al.

the above heating (hyperthermia) can be supplemented with controlled release of encapsulated drug [8, 9]. The efficiency of the MF-energy conversion into thermal energy can be increased using nonspher-ical (e.g., cubic) nanoparticles introduced into the capsule shell [10].

Another problem that can be solved with the aid of magnetic particles introduced into a capsule with drug is the activation of such a capsule. In particular, a pulsed M F of 0.18 T has been used in [ 11 ] for effect on magnetic colloidosomes. The resulting iterative compression has led to liberation of encapsulated substance. Such a procedure provides stable release controlled by compression and relaxation cycles of colloidosomes but the capsules with a diameter of up to 500 \xm are too large for drug delivery in vivo. AC MF is a universal external effect that provides opening of magnetic microcapsules in biomedical applications. Human body tissues are transparent for such an effect and are not damaged. Effect of low-frequency MF on the capsule at the desired location leads to rotational or vibrational motion of magnetic particles in the capsule shell and conversion of the MF energy into mechanic energy. The motion of particles leads to local or complete destruction of the capsule shell and drug release. Such a problem has been solved with the aid of magnetic (e.g., magnetite [12]) nanoparticles with almost spherical shapes that are evidently nonoptimal. Several additional problems must be solved for fabrication of magnetic particles for biomedical applications. In particular, a protecting layer may be needed on the surface of a magnetic nanoparticle. Electrodeposition has been used to fabricate iron nanowires (NWs) with a length of 15 |im (polycrystal-line) or 1 jam (single-crystalline) in the pores of porous aluminum oxide with a diameter of 50 nm [ 13]. Further oxidation (in a template at a temperature of 150°C and time ranging from 10 min to 72 h) has been used for fabrication of the F304 oxide layer on the surface. Such an oxide layer prevents further oxidation of NWs at room temperature. The resulting "core—shell" structures have been studied using methods of magne-tometry and magnetic force microscopy. It has been shown that the magnetic properties strongly depend on the conditions for preparation and shell thickness (the saturation magnetization and residual magnetization decrease with increasing thickness). Note also that the NWs with oxide shells exhibit higher biocom-patibility.

A general review of the application of magnetic particles in therapy and diagnostics and the corresponding problems have been reviewed in [14]. It has been shown that the energy effect of MF on a biochemical system can be enhanced using magnetic nanoparticles (MNPs) that serve as mediators of the field effect. While inside organism, MNPs become primary targets for the M F effect providing high sensitivity of the system to external MFs. MNPs provide, first, enhancement (by several orders of magnitude) of

the MF effect and, second, localization of such an effect in the desired region (provided that the MNPs are delivered to this region). Thus, the total intensity of the external action can be decreased and the effect can be localized. For such purposes, MNPs are function-alized using one or several shells containing the specified bioactive substance (ligand shells). Normally, the radius of such a functionalized particle is up to 100 nm. In addition, such shells protect MNPs against oxidation and provide the required hydrophobic properties that prevent aggregation and diminish cytotoxicity. Such MNPs with ligand shells can be supplemented with the capsules that contain a bioactive substance in the central part surrounded with shells containing magnetic particles (the radius of such nanocapsules is up to 100-300 nm). In the presence of external field, magnetomechanical activation of MNPs takes place: depending on the field (dc-ac and uniform—nonuniform), the MNPs may exhibit rotational, transla-tional, rovibrational, or translational-vibrational motion. Such motion may lead to local heat liberation or destruction of the capsule. Evidently, such an effect depends on the parameters of the external magnetic field.

In the above scenarios, particles have uncontrolled (normally, almost spherical) shapes. In this work, we propose functionalization of polymer capsules using elongated magnetic nanosized particles (cylindrical MNPs (CMNPs)). Application of such particles with a predetermined aspect ratio and controlled magnetic moment makes it possible to solve the problems of both targeted drug delivery and controlled opening of polymer capsules due to mechanical damage (destruction). Such damage can be due to rotation of magnetic particles (located inside the capsule shell) in the presence of ac magnetic field with a certain frequency. In this work, we use nanosized fragments of NWs as magnetic particles. The approach is based on fabrication of heterostructure NPs consisting of layers of magnetic metal (Ni) with the specified length that are spaced by Cu metal layers, which must be removed afterwards (sacrificial layers). Such NPs can be obtained with the aid of template-assisted synthesis based on electrochemical filling of track membranes. The principles of the membrane-based synthesis can be found in [15]. Fabrication of layered NPs (variant of the above structures) has been described in several works. State of the art, in particular, specific features of fabrication of layered NPs has been presented in monograph [16]. A method for fragmentation of the layered NPs has been proposed in [17]. However, the fragmentation has been performed for NPs preliminary fixed on the surface for alternative purposes. We have discussed several particular problems of fabrication of long NWs consisting of nickel and copper layers and control of the layer thickness in [18]. The process has been performed in electrolyte containing ions of both metals. Alternation of metal layers has been implemented using periodic changes of the growth voltage. After

TECHNICAL PHYSICS Vol. 65 No. 9 2020

removal of the growth polymer template, the samples have been studied using SEM and TEM methods that have shown alternation of layers with different compositions. The task of this work is to develop a method for fragmentation of such NWs using selective etching. The final task is to obtain calibrated (with respect to size) elongated CMNPs and study such particles included in the shells of multilayer polyelectrolyte microcapsules.

500 nm

Fig. 1. SEM image of the suspension of layered NPs.

1. EXPERIMENTAL 1.1. Materials and Methods

Track membranes from Joint Institute for Nuclear Research were used as growth matrices. The thickness of the polyethylene terephthalate (PETP) membrane is 12 \xm, the pore diameter is 100 nm, and the pore density 1.2 x 109 cm-2. For electrodeposition, a thin conducting copper layer is sputtered on one side of the matrix with the aid of thermal vacuum sputtering (VUP-4). Then, the sputtered layer is galvanically fixed (CuS04 • 5H20, 200 g/L and H2S04, 10 g/L) to form a continuous conducting layer that serves as a working electrode. For electrodeposition, we use the following composition of electrolyte: NiS04 • 7H,0, 0.7 M; CuS04 • 5H20, 0.025 M; and H3B03, 0.51 M (where M is mol/L). A galvanic cell with an area of the deposited sample of 2.5 cm2 has been constructed at the Design Bureau of the Crystallography and Photonics Research Center. An El ins P-2X potentiostat— galvanostat served as the current source for electrodeposition. The device allows time recording of the galvanic process.

For fabrication of polymer microcapsules (PMs), we use the following materials and reagents: calcium chloride CaCl2, sodium carbonate Na2C03 from Acros Organics, polyallylamine hydrochloride (PAH), sodium chloride NaCl, trisodium salt of ethylenedi-amine tetraacetic acid (EDTA), polysorbate 80, and tannin acid from Sigma-Aldrich. In the experiments, we use the deionized water obtained with the aid of the Millipore Milli-Q Plus device.

The sizes and morphology of the CMNPs and PMs were studied with the aid of SEM using the JCM-6000plus device equipped with a unit for elemental analysis and JSM- 7401F device (JEOL, Japan). Both devices worked in the regime of secondary electrons.

The zeta potentials on the PM surface in suspension were measured using a Malvern Zetasizer Nano ZS computerized analyzer at a temperature of 25°C.

1.2. Experimental Results

NWs were layer-by-layer electrodeposited in the pores of the track membranes. The electrodeposition involves deposition of nickel layers (magnetic layers to be extracted as single CMNPs) and copper (sacrificial) layers. Such an approach allows synthesis of mul-

tiple CMNPs in a single pore channel. Sequential deposition of different metals was implemented using sequential changes of the potential in the course of growth. The potentials for copper and nickel layers are 0.7 and 1.8 V, respectively [18].

The SEM method was used to monitor the formation of the heterostructure NWs. Prior to the measurements, the NWs were separated from the growth polymer matrix and, then, NWs were separated from the copper substrate using an ultrasonic bath. Note that preliminary experiments were performed for NWs consisting of copper and cobalt layers, since such a combination of metals makes it possible to obtain relatively high contrast in microscopic analysis. Figure 1 shows an example of the SEM image obtained for a suspension of the layered NWs.

The SEM image clearly shows single layers. We also analyzed different growth regimes. In the best regime with respect to exact control of the thickness of deposited layers, the potential depends on the charge flow (such a study has been started in [19]). Two regimes were used: the thicknesses of the nickel layers were 200 and 400 nm, respectively, and the thickness of copper layers was 100 nm in both cases. The numbers of the deposition periods were 10 and 5, respectively. After the electrodeposition, the matrix was removed in concentrated alkali NaOH at a temperature of 60°C and a time of 2 h. The task of the next stage was the fragmentation of the layered NWs. The problem was solved with the aid of removal of sacrificial layers and copper substrate using selective etching. In this work, we tested four etching agents. The first one is the solution of NH4OH (150 g/L) in water with CuS04 • 7H20 (1 g/L). Such a solution dissolves copper and does not react with nickel. The main disadvantage is a relatively long etching time (about 72 h at room temperature). To accelerate the process, we used a solution of citric acid (300 g/L) and NaCl (50 g/L) in H202. A disadvantage of the method is related to violent reaction with copper and slower reaction with

TECHNICAL PHYSICS Vol.65 No. 9 2020

(b)

Zeta potential distribution

-100

Total counts, 104 40

30

20

10

0

Total counts, 104 (a)

Zeta potential distribution

60 50 40 30 20 10 0

0 100 200 Apparent zeta potential, mV

-100

0 100 200 Apparent zeta potential, mV

Fig. 4. Zeta potential of CMNPs with lengths of (a) 200 and (b) 400 nm.

electrolyte. In this work, we fabricated capsules with the following composition of the shells: PAC/PSS/PAC/NP/PSS/PAC/PSS. After deposition of the desired number of layers 0.2 M EDTA solution with pH 7.5 was added to the suspension for dissolving of the CaC03 particles. After 15-min-long incubation with EDTA, the capsules were thrice washed with water. The resulting capsules were stored as an aqueous suspension at a temperature of 4°C.

The CMNP were incorporated into the shells of polymer capsules with the aid of electrostatic adsorption. For optimization of the procedure, we measured the zeta potential, which appeared to be —8 ± 2 and -4 ± 1 mV for CMNPs with lengths of 200 and 400 nm, respectively (Fig. 4). With allowance for the negative surface charge, we performed adsorption of CMNPs on a layer of positively charged electrolyte.

Table 1 presents the zeta potentials for the CaC03 particles with polyelectrolyte layers. Switching of the charge polarity due to alternation of polyanion and polycation characterizes the layer-by-layer formation of the capsules. When the CMNP layer is deposited, the zeta potential changes sign, which indicates efficient adsorption of particles on the PAC layer.

Samples of capsules with CMNP lengths of 200 and 400 nm have equal (within experimental error) zeta potentials. Such a result proves the absence of the effect of NP sizes on the stability of capsules.

The SEM study proves the presence of CMNPs in the capsule shells (Fig. 5).

The SEM images show that the CMNPs are incorporated in the polymer shell, which was the purpose of this work. Note nonuniform distribution of particles, presumably, due to aggregation. To further suppress the aggregation and improve the surface properties, the CMNPs were coated with surfactants. The analysis of the SEM images of the capsules formed with application of modified CMNPs shows that the surface modification slightly suppresses the aggregation of particles and does not affect the efficiency of the CMNP incorporation into the polyelectrolyte shell.

Further optimization of the CMNP incorporation in the shell will be based on a search for more efficient methods for suppression of strong aggregation including passivation and temporal transition to nonmagnetic state (e.g., due to heating).

Table I. Changes of zeta potential upon formation of polyelectrolyte capsules

Sequence of layer deposition Zeta potential, mV

CaC03 0 ± 1

CaC03/PAC 3 ± 1

CaC03/PAC/PSS -22 ±2

CaC03/PAC/PSS/PAC 7 ± 2

CaC03/PAC/PSS/PAC/N P NP 200 nm NP 400 nm

-24 ±2 -12 ± 1

CaC03/PAC/PSS/PAC/NP/PAC/PSS/PAC 6 ± 2 5 ± 1

PAC/PSS/PAC/NP/PAC/PSS/PAC capsules after dissolution of CaC03 8 ± 2 7 ± 1

TECHNICAL PHYSICS Vol.65 No. 9 2020

14. Yu. I. Golovin, N. L. Klyachko, A. G. Majouga, M. V. Efremova, M. M. Veselov, K. Yu. Vlasova, A. D. Usvaliev, I. M. Le-Deygen, A. V. Kabanov, S. L. Gribanovskii, D. Yu. Golovin, A. O. Zhigachev, and A. V. Shuklinov, Nanotechnol. Russia 13 (5—6), 215(2018).

15. C. R. Martin, Science 266 (23), 1961 (1994).

16. Magnetic Nano- and Microwires: Design, Ed. by V. M. Woodhead (Elsevier, 2015).

17. H. Yao, L. Xie, Y. Cheng, J. Duan, Y. Chen, S. Lyu, Y. Sun, and J. Liu, Mater. Des. 123 (5), 165 (2017).

18. O. M. Zhigalina, I. M. Doludenko, D. N. Khmelenin, D. L. Zagorskiy, C. A. Bedin, and I. M. Ivanov, Crys-tallogr. Rep. 63 (3), 480 (2018). https://doi.org/10.1134/S1063774518030379

19. D. L. Zagorskii, I. M. Doludenko, D. A. Cherkasov, O. M. Zhigalina, D. N. Khmelenin, I. M. Ivanov, A. A. Bukharaev, D. A. Bizyaev, R. I. Khaibullin, and S. A. Shatalov, Phys. Solid State 61 (9), 1634 (2019). https://doi.org/10.1134/S1063783419090282

Translated by A. Chikishev

TECHNICAL PHYSICS Vol.65 No. 9 2020

Приложение 5: статья «Aspects of Pore Filling in Synthesis of FeNi Alloy Nanowires Using Track-Etched Membranes»

ISSN 2075-1133, Inorganic Materials: Applied Research, 2022, Vol. 13, No. 2, pp. 531-535. © Pleiades Publishing, Ltd., 2022.

Russian Text © The Author(s), 2021, published in Perspektivnye Materialy, 2021, No. 8, pp. 74-80.

ISSN2075-1133, Inorganic Materials: Applied Research. 2022, Vol. 13. No. 2. pp. 531-535. © Pleiades Publishing. Ltd.. 2022. Russian Text © The Authorfs), 2021, published in Perspektivnye Materialy, 2021, No. 8, pp. 74-80.

Aspects of Pore Filling in Synthesis of FeNi Alloy Nanowires Using Track-Etched Membranes

I. M. Doludenko"A

"National Research University Higher School of Economics, Moscow, 101000 Russia bFederal Scientific Research Centre Crystallography and Photonics, Russian Academy of Sciences, Moscow, 119333 Russia

e-mail: [e-mail] Received January 27, 2021; revised February 17, 2021; accepted February 18, 2021

Abstract—Fe—Ni alloy nanowires (NWs) with the elemental composition similar to permalloy (20 wt % iron and 80 wt % Ni) are prepared by template-assisted synthesis using track-etched polyethylene terephthalate membranes (pore diameter of 100 nm) as the template. To obtain a solid contact at the pore bottom, the template matrix is specially prepared for electrodeposition of the metals into its pores. The NW growth kinetics is studied, and the dependence of NW length on the deposition time is established. The morphology and geometry of synthesized NWs is studied by scanning electron microscopy. The NW growth rate is shown to change at different stages of matrix pore filling and vary nonlinearly. The current efficiency is calculated at the different stages of matrix Filling, and changes in this parameter correlate with the variation of growth rate. Possible explanations of the nonlinear behavior of growth rate are provided. The dependence of average NW length on deposition time is described by an equation obtained by the method of linear interpolation.

Keywords: template synthesis, track-etched membranes, electrodeposition, nanowires, growth kinetics DOI: 10.113 4/S207511332 2020125

INTRODUCTION

Currently, there is a considerable interest in developing new methods for synthesis of different types of nanostructures and studying their structural aspects and properties. One-dimensional nanostructures such as nanowires (NWs), nanorods, and nanothreads display a set of unique properties [1—3]. Templateassisted (matrix) synthesis is a common method for preparation of such structures [4]. Essentially, in this method, regular-shaped pores, which are through holes in a special-purpose matrix, are filled with material of interest. Porous aluminum oxide (PAO) [5] and track-etched membranes (TMs) [6] are frequently used as the matrix. These two types of matrices have different properties. As an example, PAO can be prepared with a high pore density, but the possibility to simultaneously manipulate the pore diameter and pore density is quite limited. Further, attempts to fabricate PAO matrices with strictly cylindrical pores were unsuccessful [7], which is another limitation of this material. Despite random distribution of pores in polymer TMs and their possible overlaps, unique features of these materials include flexibility and the possibility to purposely manipulate the pore shape; in addition, their pore density and diameter can be varied independently in a broad range.

In this work, we performed electrolytic deposition of iron and nickel in pores of TMs used here as tem-

plates, with the composition of electroplated material corresponding to permalloy.

NWs made of this type of structures attract interest owing to their potential use in medicine as components of electromagnetic wave transmitters and/or receivers, memristors, and flexible microelectronics, among other things.

Single-metal NWs had been fabricated already in first studies dedicated to template synthesis. For instance, cobalt and nickel replicas were obtained (probably for the first time) in pores of an oxide matrix [8], and such structures were proposed for use in high-density magnetic storage. Subsequently, techniques were developed to prepare NWs with more complex composition, i.e., so-called alloyed and layered NWs. The possibility to create such diverse structures is a unique feature of the method of electrochemical deposition [9—11].

Fe—Ni and Fe—Co NWs were compared in a number of studies. The magnetic behavior of the two types of alloys was found to depend on the ratio of alloy components and their orderliness [12]. Further, conditions required for synthesis of layered NWs were also reported. Synthesis of Fe—Co and Fe—Ni NWs was carried out in POA pores and the resulting materials were compared [13]. Distinctions between the properties of the two types of electrodeposited NWs were identified, and the effect of thermal treatment on their

531

structure was established. Specifically, it was revealed that coercive force Hc in the Fe—Ni NWs increases with increase in their length, whereas the opposite effect was observed for the Fe-Co NWs. Annealing did not affect the magnetic behavior of Fe—Ni samples, whereas a considerable increase in coercive force was detected in Fe—Co samples. We note that POA was used as the template matrix in the overwhelming majority of published studies. With TMs, however, there is an additional possibility to manipulate the pore shape and size and create components for flexible electronics. FeCo and FeNi NW arrays synthesized in pores of polyethylene terephthalate matrices were studied in [14—16]. Growth patterns observed in deposition using a two-electrode configuration were established along with the influence of pore diameter. In the studies cited, Mossbauer spectroscopy was used to reveal the orientation of the magnetization vector within the NW arrays, and, in particular, in samples with pores of small diameter, the magnetization vector was found to be oriented along the NW axis. With increase in the pore diameter and/or decrease in the deposition voltage, the parameters of Mossbauer spectra of resulting samples were fairly similar to those of corresponding bulk materials. The same method was used for indirect determination of NW metal content. Studies of the magnetic properties of NW showed that Hc and remanence increased in response to a decrease in the pore diameter or an increase in NW growth rate. The effect of anomalous codeposition of iron was revealed in [17], and it was further shown that the ratio of constituent metals in NWs may vary lengthwise. These problems, however, were not addressed in detail in the cited study.

The literature survey showed that, in particular, the issue with rigorous control of pore filling in TMs and filling kinetics has been little studied.

The aim of this work was to study the NW growth rate and current efficiency at different stages of matrix template filling. This study will make it possible to fabricate NWs with precise dimensions.

EXPERIMENTAL

NWs studied in this work were prepared using commercial polymer matrices, i.e., TMs ("nuclear filters"), with through pores with cylindrical cross sections (Joint Institute for Nuclear Research, Dubna, Russia) and the following specifications: pore diameter, 100 nm; filter thickness, 12 (am; and pore density, -1.2 x io9 cm"2. An electrically conducting layer on the membrane surface was created by plating a metallic layer in two stages. At the first stage, a thin amorphous copper sublayer (50 nm) was created by thermal sputtering in vacuum using a VUP-4 unit, with the layer not closing pores of the polymer matrix. To close the pores completely and create a continuous, solid contact layer, a copper layer with a thickness of

4-5 |im was electroplated galvanostatically onto the sputtered sublayer by applying a current density of 71 A/cm2 for 30 min.

NWs were created by electrodeposition into pores of a template matrix using a plating bath composed of NiS04 • 7H20 (16 g/L), NiCl2 • 6H20 (40 g/L), and FeS04 • 7H20 (8 g/L). Similarly, the following additives to the bath were used: boric acid (H3B03,25 g/L; to maintain pH 2.4), sodium lauryl sulfate (1 g/L; to improve wettability of matrix pores), and ascorbic acid (1 g/L; to prevent ferrous ions from oxidation to ferric ions).

The process was carried out in a dedicated cell. The surface area of a TM involved in electrodeposition was 1.8 cm2, and thus the area of working electrode, i.e., the surface area of matrix pores, was 0.17 cm2. Electrodeposition was performed in the potentiostatic mode at a potential of 1.5 V using an iron anode and an Elins P-2X potentiostat/galvanostat to control the applied potential. In our previous work, we carried out a detailed study of the relationship between the structure of Fe—Ni and Fe—Co nanowires and the electrodeposition conditions such as electrolyte composition and applied potential [18]. The adopted deposition conditions enabled us to produce NWs of a Fe—Ni solid solution based on the Ni lattice with the Fe : Ni ratio of 24 : 76.

Prepared samples were studied by scanning electron microscopy (SEM) on a JSM-6000Plus instrument (JEOL) operated in the secondary electron mode at an accelerating voltage of 15 kV.

EXPERIMENTAL RESULTS AND DISCUSSION

In this study, TMs filling was carried out potentio-statically at a potential of 1.5 V using an iron anode to make up for the loss of iron ions in the electrolyte and different deposition times. Initially, a current transient (a characteristic of electrodeposition process) for the entire process was recorded to determine the time required for matrix filling (Fig. 1).

As can be seen, the process of matrix filling can be divided into five stages: (1) the onset of NW growth, when the current decreases following the Cottrell law [19]; (2) filling of matrix pores and subsequent development of a diffusion layer; (3) outgrowth of deposited metal on the surface of the matrix; (4) complete filling of the matrix; and (5) formation of a continuous metal layer on the surface of the matrix.

Two series of samples differing in the deposition time were prepared to study the kinetics of filling of matrix pores: one without overgrowth and the other with overgrowth, i.e., in the latter case, the deposited metal overfilled the pores to form "caps" on the surface of the matrix [20]. The samples were then mounted on a special holder to enable SEM characterization of their face ends. For microscopic studies, samples without overgrowths were prepared by remov-

INORGANIC MATERIALS: APPLIED RESEARCH Vol. 13 No. 2 2022

Table 1. Results of calculations of the amount of charged passed, growth rate, and current efficiency

Process characteristics Growth time, s

50 100 150 200 250 300 400 500 600 650

Charge passed, C 0.8 2.1 2.6 4.1 4.3 6 7.1 9.4 11.4 12.4

NW length, |im 0.98 1.6 2.56 4 5.36 6.8 9.3 10.6 11.2 11.5

Growth rate, nm/s 19.6 12.4 19.2 28.8 27.2 28.8 25 13 6 6

Current efficiency 58.7 14 46 46.3 59.3 53.4 62.0 53.3 46.5 44

60%, with their number increasing as the process continues.

The NW length obtained from the results of SEM study and the calculated amount of charge, growth rate, and current efficiency are reported in Table 1.

The presented results imply that both the growth rate and amount of charge passed vary nonlinearly with deposition time. Changes in the current efficiency correlate with changes in the growth rate. The time dependence of the growth rate at different stages of pore filling is presented in Fig. 3 to give a visual idea of the results under discussion.

Presumably, the high growth rate observed during the first stage (0—50 s) is due to a current jump at the onset of deposition and the high concentration of electrolyte near the deposition surface. Within the time interval of 50 to 100 s, the electrolyte near the deposition surface suddenly becomes depleted. The subsequent linear increase in the growth rate (100—200 s) is related to the growth of the diffusion layer until it reaches pore openings at the matrix surface. This is followed by the formation of a common diffusion layer, which involved all pores, and the growth rate establishes and remains constant until local overgrowths emerge to form caps at the surface of the matrix. As the process continues, the deposition predominantly occurs at the caps owing to their larger surface area and the shorter distance to the anode, which causes the NW growth rate in matrix pores to diminish.

The following equation obtained by interpolation of the data presents the time dependence of average NW length before overgrowths emerge:

where t is the growth time (s) and H is the NW length (|im).

This dependence was confirmed by experiment.

CONCLUSIONS

The growth kinetics of Fe24—Ni76 alloy NWs was studied, and key growth stages were identified.

The growth rate was found to change nonlinearly at different stages of pore filling, presumably, owing to diffusion of metal ions occurring within the confine-

ment of pore volume, which leads to the development of a diffusion layer and ultimately establishment of a constant NW growth rate.

An equation presenting the length of growing NWs as a function of the NW deposition time was obtained on the basis of experimental data. The calculated current efficiency of NWelectrodeposition was 48.4%.

FUNDING

This work was performed with partial support from the Ministry of Science and Higher Education of Russia within a state assignment to the Federal Scientific Research Centre (FSRC) Crystallography and Photonics, Russian Academy of Sciences (RAS).

Scanning electron microscopy studies were performed using the facilities of the Centre for Collective Use of FSRC Crystallography and Photonics, RAS.

CONFLICT OF INTEREST The author declares that he has no conflicts of interest.

REFERENCES

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3. Eliseev, A.A. and Lukashin, A.V., Funktsionalnyemate-rialy (Functional Nanomaterials), Tret'yakov, Yu.D., Ed., Moscow: Fizmatlit, 2010.

4. Martin, C.R., Nanomaterials: A membrane-based synthetic approach, Science, 1994, vol. 23, no. 266, pp. 1961-1966.

5. Masuda, H. and Fukuda, K., Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina, Science, 1995, vol. 268, no. 5216, pp. 1466-1468.

6. Frolov, K.V., Zagorskii, D.L., Lyubutin, I.S., et al., Synthesis, phase composition, and magnetic properties of iron nanowires prepared in the pores of polymer track-etched membranes, JETP Lett., 2014, vol. 99, no. 10, pp. 570-576.

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7. Petukhov, D.I., Napolskii, K.S., and Eliseev, A.A., Permeability of anodic alumina membranes with branched channels, Nanotechnology, 2012, vol. 23, art. ID 335601.

8. Kawai, S. and Ueda, R.J., Magnetic properties of anodic oxide coatings on aluminum containing electrode-posited Co and Co—Ni, J. Electrochem. Soc., 1975, vol. 122, no. l,pp. 32-36.

9. Lupu, N., Electrodeposited Nanowires and Their Applications, Croatia: InTech, 2010. https://www.inte-chopen.com/chapters/8903

10. Vazquez, M., Magnetic Nano- and Microwires: Design, Synthesis, Properties and Applications, Woodhead, 2015.

11. Davydov, A.D. and Volgin, V.M., Template electrode-position of metals. Review, Russ. J. Electrochem., 2016, vol. 52, no. 9, pp. 806-831.

12. Alonso, J., Khurshid, H., Sankar, V., Nemati, Z., Phan, M.H.,Garayo, E.,Garcia, J.A.,and Srikanth, H., FeCo nanowires with enhanced heating powers and controllable dimensions for magnetic hyperthermia, J. Appl. Phys., 2015, vol. 117, no. 17, art. ID 17D113.

13. Steven, S.-L. Zhang, Z., Zhou, Y., Li, D., Heinonen, O., Kalska-Szostko, B., Klekotka, U., and Olszewski, W., Mode coupling in spin torque oscillators, J. Magn. Magn. Mater., 2019, vol. 484, pp. 227-242.

14. Zhou, S., Wang, C., Zheng, C., and Liu, Y., Manipulating skyrmions in synthetic antiferromagnetic nanowires by magnetic Field gradients, J. Magn. Magn. Mater., 2020, vol. 493, pp. 165740-165743.

15. Frolov, K.V., Zagorskii, D.L., Lyubutin, I.S., et al., Magnetic and structural properties of Fe—Co nanow-

ires fabricated by matrix synthesis in the pores of track membranes, JETPLett., 2017, vol. 105, no. 5, pp. 319326.

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16. Zagorskiy, D.L., Frolov, K.V., Bedin, S.A., et al., Structure and magnetic properties of nanowires of iron group metals produced by matrix synthesis, Phys. Solid State, 2018, vol. 60, no. 11, pp. 2115-2126. https://doi.org/10.1134/S1063783418110367

17. Frolov, K.V., Chuev, M.A., Lyubutin, I.S., Zagorskii, D.L., Bedin, S.A., Perunov, I.V., Lomov, A.A., Artemov, V.V., Khmelenin, D.N., Sulyanov, S.N., and Doludenko, I.M., Structural and magnetic properties of Ni—Fe nanowires in the pores of polymer track membranes, J. Magn. Magn. Mater., 2019, vol. 489, art. ID 165415.

18. Doludenko, I.M., Zagorskii, D.L., Frolov, K.V., et al., Nanowires made of FeNi and FeCo alloys: Synthesis, structure, and Mossbauer measurements, Phys. Solid State, 2020, vol. 62, no. 9, pp. 1639-1646. https://doi.org/10.1134/S1063783420090061

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Translated by A. Kukharuk

SPELL: OK

INORGANIC MATERIALS: APPLIED RESEARCH Vol. 13 No. 2 2022

Приложение 6: Статья: Electrical properties arrays of intersecting of nanowires obtained in the pores of track membranes

Electrical properties arrays of intersecting of nanowires obtained in the pores of track membranes // I.M. Doludenko, I.S. Volchkov, B.A. Turenko , I.O. Koshelev , P.L. Podkur, D.L. Zagorskiy, V.M. Kanevskii. Materials Chemistry and Physics 287 (2022) 126285

doi: https://doi.org/10.1016/j.matchemphys.2022.126285. Q2

out. In this regard, investigations of the structural features and properties of nanowires of various types, as well as methods for their preparation, are of considerable interest. There is a number of methods for obtaining of nanowires, such as thermal or laser deposition [11,12], which are well suitable for the obtaining of semiconductor nano-structures, and classical methods such as vapor-liquid-solid obtaining [13,14]. Also, a widespread method of obtaining nanostructured materials from metals and alloys is matrix synthesis [15]. The main idea of it is to fill a previously prepared matrix with the required substance. Porous oxide of aluminum (POA) [16,17] and track polymer membranes (TM) [ 18-20] are the most often to be used as a matr ix for synthesis of nanowires with a large aspect ratio. POA matrices are distinguished by a high density of pores with a regular geometric arrangement; however, it is difficult to simultaneously change both the density of pores and their diameter. Also, in POA matrices, there is a certain scatter in the shape of pores, several percent of which are not strictly cylindrical and vertical [21]. Polymer TM are characterized by a chaotic arrangement of pores with the possibility of overlapping one another, however, they differ in flexibility and the ability to purposefully change the shape and diameter of the pores, while the difference in the shape of the pores from each other. In addition, in TM it is possible to vary the density of pores over a wide range, regardless of their- diameter and location. A significant difference of TM is the possibility of changing the angle of inclination of the pores to the normal of the polymer film, as well as increasing then-density while maintaining the diameter along the entire length.

It is possible to obtain nanostructures of pure metals [22,23] and complex compositions, such as alloys or layered nanowir es [24,25] by the matrix synthesis. Thus, nanowires made of Fe-Co, Fe-Ni alloys have magnetic properties depending on the configuration of the received nanowires. These materials ar e promising for materials for medicine and can also find their application as components of sources and receivers of electromagnetic waves, memristors, elements of flexible microelectronics and others [20,26-30]. In a number of papers, comparison of nanowires from these alloys was made. Thus, in Refs. [27-30] the magnetic properties of nanowir es made of alloys obtained by using a POA matrix were investigated and the dependence of the proper ties on the ratio of elements in the nanostructures, their- ordering, and the effect of heat treatment on the structure was shown. The magnetic properties of nanowir es depended on the lengths of the synthesized nanostructures.

However, in described works, due to the limitations introduced by the manix material, it is impossible to pr operly assess the effect of the degree of pore filling on the physical properties of the obtained arrays of nanowires. It is possible to determine this dependence when using TM as a matrix. Thus, in Refs. [20,31,32], arrays of Fe-Co and Fe-Ni nanowires synthesized in the pores of a polyethylene terephthalate (PET) matrix were studied. Regularities of synthesis were determined for a two-electrode deposition scheme, and the effect of the pore diameter on the or ientation of the magnetization vector of nanostructures array and its magnetic properties were shown. However, the use of arrays of nanowires as components of flexible electr onics and arrays of sensors or nanoscale circuits [23] requires detailed investigation of the electrical properties of these arrays of nanowires, including the dependence of their" electr ical proper ties on the length of nanowir es and on the structure of the entire ar ray of nanowir es. Thus, the aim of this work was to study the electrical properties of arrays of Fe-Ni alloy nanowires of various lengths in pores with a diameter of 100 nm in a PET matr ix, as well as to assess the possibility of controlling the electr ical pr oper ties of the obtained arrays by changing the nanowire lengths and the configuration of the entire array.

2. Experimental

The arrays of Fe-Ni nanowires of various lengths obtained by electrochemical deposition into the pores of track etched membranes made of PET were studied. The pores in the matrix were thr ough and had a cylindrical shape. The industrial track membranes manufactured by

JINR (Dubna, Russia) were used, the par ameters of the membr anes were as follows: pore diameter (d) - 100 nm; film thickness (h) - 12 (.un; pore density (N) - 1.2109 pores/cnr; angular distribution of pores ±30 along the cour se of rolling the film (vertically) dur ing ir radiation with ions and ±0.5: perpendicular to the course of rolling the film (horizontally) along the course of the scanning ion beam. The process of obtaining of tr ack etched membranes is described in details in Refs. [33, 34].

The preparation of the matrix for the deposition of metal into the pores was made in several stages, shown in Fig. 1. The filling of the pores of the manix and the production of nanowires were carried out according to the method described in Ref. [35]. The elecUodeposition process was carried out in a special galvanic cell. The area of the TM involved in the deposition process was —1.8 cm2. The area of the working elecfrode was 0.17 cm2 and approximately corresponded to the surface area of the pores of the matrix. A potentiostat/galvanostat "Elins P-2X" was used as a current sour ce. The process was carried out in the potentiostatic mode. The deposition potential was 1.5 V. An iron anode was used for the Fe ions compensation. In Ref. [34], the authors showed that the above-described deposition mode makes it possible to obtain nanowires consisting of an Fe-Ni solid solution based on a Ni lattice with an element ratio of ^Fe24-Ni76- Arrays of nanowir es of different lengths were obtained by changing the time of the elecUodeposition process, according to the previously obtained dependence of the average length of nanowir es on time, for pores with diameters of 100 nm [36]:

/=410-9-r3 + 310-5-/2+0.0128r (1)

where t - time of electrodeposition, s; I - average nanowire length, |im.

A JSM 6000 PLUS (Jeol, Japan) scanning electr on microscope (SEM) was used to control die average length of the deposit arrays of nanowir es and to determine the distribution of pores over the sur face of TM. The study was carried out in the secondary electron detecting mode at an accelerating voltage of 15 kV.

The elecnical characteristics of the nanowir e arrays were measured using a resistivity control unit Cresbox (Napson, Japan) using the standard four-probe DC method [37]. The measuring probes were made of tungsten carbide, the distance between adjacent probes was 1 mm, the radius of the tip rounding was —150 pm, the load on the measuring needle was 50 g. When measuring the elecnical characteristics, the contact of each probe with the sample sur face was car ried out over an area of ^0.710 5 cm2. Thus, each probe was in contact not with a single nanowire, but with an array consisting, on average, of 8500 nanowires. The determination of the r esulting r esistance of the samples under study was car ried out at 250 points, evenly distributed over the surface of each sample, in order to obtain aver aged values of the resistances of the entir e array of nanowir es, as well as to level the contribution of the disordered arrangement of pores.

3. Results and discussion

3.1. Matrix characterization

Analysis of the pore disUibution over the sur face of the PET matrix was carried out to characterize the TM which was used in the work. For this sake, a series of SEM images were made in different parts of the sur face of the PET matrix (Fig. 2). The analysis of the pore disnibution over the surface was car ried out using the single bond method ("nearest neighbor" method) [38-40]. So, the average distance from the center of the pore to the center of the nearest pore was determined by the formula:

M= X/'A (2)

where r,- distance from the center of a pore to the center of the nearest pore; n - number of pores in the analyzed area.

For the next step, the average value of rA was determined over a

themselves only at sizes on the order of interatomic distances. But, it is known that the properties of structures based on FeNi still depend on the sizes larger than interatomic [43,44]. This necessitates the introduction of the conditions for their intersections: since typical metals, as mentioned above, have a pronounced quantum size effect at extremely small sizes, the sizes of the intersection region of two nanowires can be much smaller than the sizes that show a sharp change in properties in Refs. [41,42]. In this case, it is not worth taking into account the cases when the nanowires are only slightly superimposed on each other, because of the possible manifestations of size effects when the sizes of the nanostructured regions formed are too small. In this regard, those pores in which at least 10% of their unit volume overlap will be considered as partially superimposed pores. So, it is necessary to enter the definition of a unit volume (V^ ):

Vind=n-{df2f-d (5)

where d - pore diameter.

After determining the unit volume, it is necessary to determine the projection of the area of this intersection onto the matrix surface. So, when two pores intersect, the area of their intersection has the shape of an irregular cone, having at the base, in the limiting case, two equal segments. In the case of intersection of pores in the volume, with an angular distribution of pores in the range of ±30:: relative to the surface, it can be determined, based on simple geometric calculations, that at least 30% of the pore projection areas are superimposed on the surface (the limiting case when two pores are intersected at angles of 30 and -30 ). Now, using the projection of the condition for talcing into account the intersections on the matrix surface, it can be determined that superimposed pores will be considered as those pores whose areas of exit to the surface are located within die Sprob - the maximum area that satisfies the condition of the limiting partial overlap of pores:

Spmb=n-{\5-d - 2-bf (6)

where b - difference between d/2 and the altitude of the triangle (k) at the sector formed by the intersection of pores:

k = {d-sin a)/4-sin(ar/2) (7)

where a - angle of a circular arc formed by the intersection of an adjacent pore.

3.2. Determination of pore crossing probability

Next, it is necessary to determine the probability of pore overlap on the matrix surface using the obtained SEM images. Based on the obtained SEM images (Fig. 2) of the regions of the PET matrix, the distance to 4 nearest neighbors for each pore is determined. Then the calculation of the number of pores located within circles of radius fA, where the center of each circle is the center of each pore participating in the calculation, is carried out. Knowing die number of pores in the image, as well as the distance between the center of each pore and the 4 nearest neighbors, it is possible to calculate the probability of the location of several pores in a circle with radius fA:

Pi = Ni/Ncom (8)

where P, - the probability of finding the i-th number of pores at a distance rA from the center of each pore, NCOm- total number of pores on the figure, Ni - the number of pores on the figure, at a distance rA from which there is the i-th number of pores; i - the number of pores located at a distance rA from the center of each pore. Table 1 shows the average values of the probabilities of finding the i-th number of pores in a circle of radius fA.

Next, it is necessary to calculate the probability of overlap, including partial overlap, according to the previously set condition, on top of each other in the images. To do this, it is necessary to calculate die probability

Table 1

Distribution of pores over the surface of the PET matrix, as well as the probability of their partial overlap in the subsurface layer characterized by a unit volume.

¿(pes) 1 2 3 4

100 39.3846 8.123 1.5716

- 0.22683 0.009217 0.000499

N,v. i (pes) - 1622944 17355 99

Pi Mm (%) 100 61.5804 27.7929 6.5395

0.000932 1.88699 10~6 1.16632 10 °

, „ (pes) - 9954 9 0.01

of partial overlap.

P - (Sprob\ _ « Spore •Sprob r<y.

where S^ - area of projection onto the surface of one pore; SfA - area of a circle with radius fA; Sprob - maximum area satisfying the condition of partial overlapping of pores; P^ , - the probability of superposition of the i-th number of pores in the area of radius fA.

The average number of pores satisfying the condition of partial overlap was determined by multiplying the total number of pores located on a unit area with (8) and (9):

Wsup .i=Psv.rPrN (10)

In this case, it is necessary to take into account the peculiarities of the process of irradiation of a PET matrix by ions for the formation of tracks. So, as mentioned earlier, the pores in the matrices used were located not perpendicular to the plane of the matrix, but at an angle. Moreover, if the horizontal spread of ions was ±30°, then the vertical spread did not exceed ±0.5°. As a result, the resulting pores can form intersections only horizontally, while the vertical displacement of the points of entiy and exit of the ion into the PET matrix differed by no more than 0.5 nm at a matrix thickness of 12 pm. In this case, it could not lead to the formation of any significant number of intersections in elevation projection. As a result, when assessing the probability of pore intersections in the volume, it is required to take into account the intersections only in the horizontal projection. The average distance between pores in the horizontal projection will differ significantly from the previously determined average distance to the nearest neighbor fA. To determine the average distance between the pores in the horizontal projection, one needs to split the obtained SEM images into areas with a height of 100 ± 1 nm and determine the distance between the pores in these areas for all images (example in Fig. 3). Moreover, in the calculation, pores with at least 30% of their area in the analyzed zone will be taken into account as a whole pore. Thus, the analysis of SEM images of a PET maU ix (Fig. 2) made it possible to determine the average minimum distance between the pores in the horizontal projection: fH = 0.284 pm.

After determining fH, one needs to estimate the probability of pore overlap in bounded regions over the matrix surface. To do this, the steps to detemiine the probability of finding the i-th number of pores at a distance fA from the center of each other (8) should be repeated, however, with some changes in die calculation conditions. So, instead of fA, the FH is used. Also, determination of the distance to 4 nearest neighbors is canied out only within a limited zone. Knowing the number of pores in the images (Fig. 2), as well as the distance between the center of each pore and the 4 nearest neighbors in a limited zone, it is possible to calculate the probability of the location of several pores in a circle with radius fH:

Pi lint = Ni lim/Ncan. tim. (11)

where P, ^ - the probability of finding the i pores at a distance fH from the center of each pore in limited zone; NCOm. lim. - total number of pores in limited zones; A/j the number of pores on the image in limited

I.M. Doludenko et al Table 2

Calculation of the number of intersections of up to 4 nanowires satisfying the stated condition for nanostructuies of normal length.

/(Mm)_N„oi ,3 (pes)_i\cm, 3 (pes)_\m,A (pes)

8.18 245470 2343 29.83

7.32 196798 1683 19.2

5.92 129167 896 8.3

5.77 122730 830 7.49

4.30 68762 349 2.36

4.14 63761 312 2

3.01 34040 122 0.58

2.75 28546 94 0.41

1.72 11408 24 0.06

1.05 4453 6 0.01

number of such intersections will not have any significant effect on the formation of an electrical circuit.

The total number of inter-sections and overlaps on the surface was determined as their- sum:

Ncms. res. = ¿(Ncros. i + Nsup. i h) (17)

0

The results of calculating and measuring the resistance are shown in

Table 3.

3.3. Electrical resistance of the metal-polymer composites

Resistance for each sample was measured as the average of 250 points equally spaced across the sample area. In the case of growing nanowir es to the entire thickness of the matrix, it would be necessary to take into account partial overlaps on the reverse side, but in present case this is not required, since only partial, rather than thr ough, filling of the matrix pores is performed.

Fig. 5 shows the dependence graphs of the total calculated number of intersections (Ncros res.) and reverse resistance (l/R ) on the length (/) of nanowires. It can be observed that the dependencies have a similar form, however, there are some deviation regions in dependency of reverse resistivity O/xJ on the length (0 of die nanowires. The first deviation is observed at nanowire lengths less than 2.7 |mi the formation of a continuous conducting chain is not observed, due to the lack of intersections for the formation of a stable elecnical circuit, and therefore the resistance of the manix significandy exceeds hundreds of Mil At nanowire lengths longer than «2.7 pm, a conducting chain of nanowires begins to form, sufficient enough to measure the resistance, which, with an increase in intersections and nanowir e lengths, is characterized by the gradual formation of a continuous stable conducting layer at a nanowire lengdi of >4 |mi, followed by a relatively smooth conductivity growth, the dependence of which correlates with the dependence of the growth of intersections of nanowires with an increase in their length. The results obtained demonsUate the existence of a critical nanowire length at which, in a given TM configuration, the formation of a

Table 3

Average resistance, as well as the number of wire crossings in arrays of Fe-Ni nanowires of various lengths.

i(pm) N„m m (Pes) Ravttl)

8.18 257808 9.7